Air purifiers have been a hot commodity over the past year, as people attempt to combat the fact that COVID-19 can spread through aerosol transmission. But a new study shows that some of these gadgets can create air quality problems of their own.
The study, conducted by researchers at the Illinois Institute of Technology, Portland State University, and Colorado State University, looked at a particular kind of purifier, called a bipolar ionizer, which is often marketed as a way to disinfect air from viruses like COVID-19. (Last year, Business Insider called the device a “secret weapon.”) But this study shows that while bipolar ionizing devices sound appealing, they can increase the presence of harmful volatile organic compounds (VOCs) and create side effects that far outweigh the benefits.
Researchers conducted a “field test,” for which they installed a bipolar ionizer inside an air handler (basically part of the HVAC system) in two spots: One fed into a controlled room they set up, the other into an occupied office building. Unlike air purifiers that use a filter, ionizer air purifiers disinfect air by electrically charging particles, causing bacterial, fungal, and viral particles to drop out of the air faster. They’re already installed in large buildings like airports across the country.
But should they be? There are three ways to improve the quality of indoor air, according to Brent Stephens, chair of the department of civil, architectural, and environmental engineering at Illinois Tech and a member of the research team. You can remove VOCs; kill microorganisms like bacteria or viruses; or remove particulate matter like dust or pollen. This study, published in the journal Building and Environment, looked at the first and last of these: the device’s ability to remove VOCs, and its ability to reduce particulate matter. (It did not examine the efficacy of air purifiers’ ability to filter COVID-19 virus particles.)
What it found isn’t great. “Additive technologies [like ionizing purifiers] have been marketed . . . for effectiveness, and we . . . didn’t find convincing results,” Stephens says. “And there’s a potential for by-product formation.” By that he means the device can actually increase the presence of VOCs like acetone and ethanol, which can be harmful to the eyes, nose, throat, and skin. On top of that, the device’s ability to remove particulate matter like dust, smoke, and pollen was negligible. That was enough for the researchers to encourage the use of alternative air purifiers like HEPA filters, which don’t have “this potential for a downside that we know almost nothing about,” Stephens says.
So why are bipolar ionic purification systems already installed in places like LaGuardia Airport? Stephens suspects that engineers are taking the marketed efficacy of the devices at face value. The issue is that unlike filters, electronic air cleaning devices aren’t standardized or regulated. Instead, commercial labs have conducted the studies and self-report their efficacy, often in small settings and unrealistic conditions, according to Stephens, who called such manufactured reports “an open secret.”
“I tend to find flaws in the entire additive air cleaning industry,” Stephens says, noting that these devices end up in HVAC systems because people take the products on faith, and because they’re easier to install than filters; the fact that they can add more harmful by-products to the environment just isn’t on people’s radar.
The report recommends creating a standard test method. “Without peer-reviewed research into the health impacts of these devices, we risk substituting one harmful agent for another,” Stephens warns. He says the takeaway for consumers should be to follow guidance from organizations like the American Society of Heating, Refrigerating and Air-Conditioning Engineers and stick to conventional technology that we know works.